Current forms of biological testing typically require the use of complex electronic sensors. These sensors may be costly and may prohibit the geographical coverage of the sampling, as only areas having sensors may be sampled. Environmental testing of currency, such as paper currency, may be possible. However, due to the widespread and longstanding circulation of currency, it is very difficult to determine when or where any particular contaminant was detected. Moreover, some reagents are not particularly safe for human contact, so the application of such reagents may require pulling the currency out of circulation. Cheaper and more robust environmental sampling techniques are desired.